Significance Chronic colitis and diarrhea is a well recognized syndrome in a small proportion of rhesus macaques maintained in captivity. The etiology and pathogenesis of this syndrome is not well understood, although artificial weaning of young macaques has been identified as a risk factor for development of chronic colitis in epidemiologic studies. As currently defined, this syndrome is includes persistence of diarrhea and colitis in the absence of any identifiable enteric pathogen. Objectives This spontaneously occurring disease is being evaluated as a model of inflammatory bowel disease (IBD) in humans, and for testing of novel therapeutic compounds for the treatment of IBD. Results Several novel compounds have been evaluated for efficacy in the treatment of chronic colitis in the rhesus model. One compound, GW-83X has shown potential as a therapeutic agent, achieving clinical improvement in treated animals. Future Directions Additional compounds which are analogues of GW-83X will be evaluated at various dose levels using this macaque model system. KEY WORDS rhesus macaque, colitis, therapy FUNDING Glaxo-Wellcome